This invention relates to a graphic display memory device.
A graphic display may be generated by a t.v. monitor or like raster-scan apparatus while modulating the scanner beam in accordance with the contents of a memory holding a series of digits, one for each pixel of the display. For a computer generated image, the digits are placed in the memory by a computer processor. Such computer generated images can be made up of one or more contiguous areas or `polygons` throughout which the colour or brightness of the display remains the same. These polygons may be generated by the processor identifying those memory locations which correspond to pixels at the edges or boundaries of the polygon and then `filling-in` the polygon by a seed-fill algorithm in which a pixel control digit appropriate to the required colour or brightness is entered into a location associated with a pixel within the polygon, then addressing each location associated with the adjacent pixels and putting the same digit into them, and so on until it reaches the boundary locations. As an alternative, a vector fill algorithm is used in which a series of lines are drawn extending from one to the opposite side of the polygon without pre-calculation of its shape--instead, the line lengths are successively incremented from data indicative of the slope of each edge.
Vector-fill and/or seed fill algorithms may be supplied as firmware with purchased CGI apparatus. In either case, since the processor of the apparatus has to fill in the shape on a progressive basis, ie addressing each pixel storage location in turn and entering a digit therein, the speed of filling is not as great as may be desired unless very expensive custom built display apparatus is used.